I have recently gutted a 2001 grand prix to race as a U-Car. Upon running my first race, its like the car never responded to the throttle. I had the gas pedal to the floor and the car never down shifted and felt very under powered for the entire race. I will note that the RPM guage also didn’t register (read 0 rpms). Perhaps a sensor has failed that tells the transmission to shift?
start with basics. forget about downshifting.
does car accelerate in 1st gear from a complete stop? does it move?
not asking about 1-2 shift or 2-3 shift. does it move in 1st gear?
Yes it does take off in first gear but than it appears to just peter out on tourque (almost like the car goes immediately into upper gears well before it should. It never accelerates into the upper RPMs and feels severely under powered. Maybe its not a shift thing at all…maybe its a fuel supply issue. Once during the coarse of the race, the car did appear to downshift…get into the rev limiter, and than immediately go back into an upper gear. Not sure what sensor drives the RPM guage,but that was working very intermittently as well (registering 0 RMP most of the time).
The inputs to the 4t65-e transmission are
- Gear select position
- Fluid pressure control
- controls for 2 shift selenoids, 1-2/3-4 and 2-3
- torque converter clutch variable control
- input shaft rpm (same as engine rpm presumably) and vehicle speed
- trans fluid temperature
As you seem to have a problem with the engine rpm display, that’s where I’d start. The transmission shift and torque converter control is heavily dependent on knowing it’s input shaft rpm.
It’s also possible the “underpowered” sensation you report is caused by an engine problem, not related to the transmission. It’s hard to imagine the engine computer doesn’t know the engine rpm though, and still seem to run ok.